Grinding wheels with abrasive elements of rectangular shape



Sept. 13, 1960 w. OSENBERG 2,952,103

GRINDING WHEELS WITH ABRASIVE ELEMENTS OF RECTANGULAR SHAPE Original Filed April 4, 1957 '3 Sheets-Sheet 1 Fig.3

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Fig. l2 INVENTOR Werner OSENBERG- whiu ixkb PM p 13, 1960 w. OSENBERG 2,952,103

GRINDING WHEELS WITB ABRASIVE ELEMENTS OF RECTANGULAR SHAPE Original Filed April 4, 1957 3 Sheets-Sheet 2 25 KF/gj3 32 -T 33 38 INVENT 0R Werncr 05 EN BERG BY. w Mxw rmi A1 9 Sept. 13, 1960 w. OSENBERG I 2,952,103

GRINDING WHEELS WITH ABRASIVE ELEMENTS OF RECTANGULAR SHAPE Original Filed April 4, 1957 3 Sheets-Sheet 3 i I x INVEN Y Werner OS WMwL -J /zdd' United States Patent GRINDING WHEELS WITH ABRASIVE ELEMENTS 0F RECTANGULAR SHAPE Werner Osenberg, Hindenburg-Allee, Gehrden, Germany, assignor to Bisterfeld & Stolting, Radevormwald (Rheinland), Germany Original application Apr. 4, 1957, Ser. No. 650,740,

now Patent No. 2,882,655, dated Apr. 21, 1959. Divided and this application Dec. 18, 1958, Ser. No.

Claims priority, application Germany Apr. 7, 1956' 4 Claims. (Cl. 51-209) This application is a division of my application Serial No. 650,740 filed April 4, 1957, now Patent No. 2,882,- 655, granted April 21, 1959, entitled, Grinding Wheels with Inserted Tubular Abrasive Elements.

This invention relates to a further development of flexible grinding tools of hollow cylindrical shape with heat-resisting bond composed of thermoset-ting synthetic resin.

Grinding tools have already been proposed which possess the geometrical shape of hollow cylinders with parallel side Walls. These abrasive cylinders can be of different diameters and arranged one within the other concentrically on a carrier disc. Grinding tools constructed in this manner must run at a very high working speed because the wear when working solid and hard materials increases as the Working speed decreases. An increase in the working speed beyond 90 metres per second is limited by the strength of the abrasive tubes wound from fabric webs. The wall thickness of these tubes, and especially the flange height, that is the effective abrasion height of the abrasive body forming the,

multiple-cup disc or wheel, must not exceed a certain measurement because, by increasing the effort arm on which the centrifugal forces act, the speed of rotation at which the abrasive ring burst is reduced. The multiple-step grinding rings (multiple cup discs), owing to these limits, only enable relatively small quantities of material to be ground down completely and are primarily suitable for lighter work, for example for sharpening tools, grinding Work with small machining allowance, and so forth.

In order to remove greater quantities of chips, for example when grinding the heads of railway rails, the surface of tubes and the like, it has also been proposed to use multi-step segments which have a relatively large curvature radius. To avoid undue unbalance, the in dividual segment shells must be pressed with relatively great precision. When the segments have been placed in a grinding wheel this, must be balanced.

In order to remove the above-mentioned limits to the employment of the abrasive bodies which have already been proposed, it is proposed according to the present invention to use, instead of the multi-step grinding rings of relatively large diameter and the multi-step segment bodies, tubes preferably wound from fabric webs and of small diameter with a heat-resistant bond composed of thermosetting synthetic resin, the length of these tubes being many times greater than their outer diameter, the tubes being arranged adjusable in longitudinal direction, axially, radially or at an incline to the axis of rotation of a metal carrier (grinding wheel).

The carrier may be constructed in various ways. When the grinding spindle is vertical and for medium cutting capacities, the height of the carrier may be less.

The abrasive tubes are set in recesses arranged in a circle in the carrier and are at first loosely lheld, where'- upon after starting up the rotary movement, the final clamping is eifected either by centrifugal effect or by clamping elements, those operating with plastic means being given preference. The reception apertures must correspond to the cross sectional shape of the grinding tubes. They may be provided with flutes, transverse grooves, screw threads or the like on those walls against which the grinding tubes bear under centrifugal action. The surface of the grinding tubes is also preferably profiled for the purpose of better fixing. When the complete grinding wheel is lifted off the surface to be worked, for example that of a metal sheet, readjustment of the abrasive tubes can be carried out in a very simple manner by hand.

Another possibility of employing the abrasive tubes according to the invention consists in arranging them in means of an epicyclic gear. This type of arrangement of long abrasive tubes in a rotary cylinder allows economical removal of large quantities of material by grinding. In the case of carrier cylinders of slight height and with abrasive tubes ananged parallel to the axis of rotation, their radial adjustment can be effected by inserting the grinding tubes in radially shiftable holders which are adjusted by means of two flat spirals.

To work surfaces of relatively large area, for example the surface of metal sheets, grinding rolls can be employed. Abrasive tube sections are slipped on to bolts radially fixed in rings by pinning, by internal clamping devices or the like. By assembling such rings set with four to six abrasive tube sections, grinding rolls can be formed the width of which is variable, so that they can,

be adapted to the surface to be Worked. As the width of these rings corresponds to the internal diameter of the abrasive tube sections, the paths produced during the grinding operation overlap so that no steps are formed.

on the surface of the workpiece. It is evident that the whole grinding roll may be profiled by suitably shaping the individual abrasive tube sections.

For internally working, for example tubes, the abrasive tube sections can also be fitted in levers which spread under the action of centrifugal force and are hingedly connected with a shaft rotating at a high speed. The

internal working of bores is naturally also possible with grinding rolls, the abrasive tube sections of which are preferably radially adjustable and readjustable, for example by the axial displacement of a mandrel within the roll. The two methods of internally grinding tubes can be combined, because there is an unbroken concave surface, with the method mentioned at the end of this specification which operates with loose or loosely bonded abrasive grit.

The cross-sectional shape of the abrasive tubes has a cross-sections may be of any shape, for example circular,

Patented Sept. 13, 1960 rectangular, hexagonal and so forth; they may also be in the form of ring sections which, when fitted together, produce a circular path. If a plurality of such circular paths were to be arranged concentrically to each other, the abrasive tubes having the cross-section of one ring section are provided with spacers. The cross-section of the tubes should be so dimensioned that a suflicient quantity of abrasive material with corresponding cutting capacity can be accommodated.

With a view to producing greater abrasive tube volume increasing the chip removing capacity, the free cross-sectional area of grinding tubes of any shape can be additionally reduced by introducing more abrasive bodies. Care must, however, be taken that there is suflicient free space for leading off the larger quantities of chips produced. The additional abrasive bodies introduced can be rigidly connected with the outer abrasive tubes by welding, sticking or the like.

If very large volumes of material are to be economically removed by grinding, for example when surfacing metal sheets, grinding the inner wall of tubes and the like, the method of using tubes can, as unbroken surfaces come into question, be combined with a grinding method operating with loose grit or grit mixtures. The loose or only loosely bonded grit or grit mixtures, for example corundum and viscous bodies, is or are at the same time preferably introduced in dosed quantities in the form of cartridges, that is with thin, easily worn away metallic or non-metallic casing, into the free cross-sections of the tube and forced against the surface to be ground by exerting pressure or, according to the arrangement of the tubes, under the action of centrifugal force. An only loose bonding of the abrasive grit within the cartridge can be attained by spraying with a synthetic resin adhesive, by embedding the abrasive grit in a foam material or, likewise within the cartridge, by tightly superposing layers of, for example, abrasive paper, linen, foils, grids and stacked plates impregnated with abrasive grit. The layers can also be spirally wound and thus form the contents of the abrasive grain cartridges.

When using loose or loosely bonded grit it is advisable to feed a cooling liquid which can be conducted under pressure through the abrasive grit assemblies.

By means of wear-proof spacers, adjustable in relation to the surface engaged by the grinding tools, it is possible, as these spacers are in continual contact with the surface of the workpiece, for the end face of the tubular grinding tool to bear only lightly in relation to the unbroken, flat or concave surface, for example the inner wall of a tube, with the result that the wear of the abrasive tubes is considerably reduced. The wear-proof spacers can serve at the same time as means for measuring during the grinding operation.

Several embodiments of the invention are illustrated by way of example in the accompanying drawings, in which:

Figure 1 is a cross-sectional view through a tubular grinding tool having embedded therein abrasive bodies.

Figure 2 is a diagrammatic view showing how two concentric grinding elements are secured together.

Figure 3 is a similar view showing a modification.

Figure 4 is a similar view illustrating a further modification.

Figure 5 is a similar view with pants in cross-section illustrating a still further modification.

Figure 6 is a view similar to Figure 2 showing a still further modification.

Figures 7 and 8 are top plan and cross-sectional (diagrammatic) views respectively of a grinding device in which tubular abrasive bodies are fitted in a carrier parallel to the axis of rotation thereof;

' Figure 9 is a cross-section through the grinding device (diagrammatically illustrated), in which tubular abrasive body sections are inserted in a carrier at an incline to its axis of rotation.

Figure 10 is a top plan view of a grinding device in which the pitch circle of the tubular abrasive tools can be varied by means of flat spirals;

Figure 11 shows a cross-section through a grinding device in which the tubular abrasive tool sections are arranged radially and fixed on pins of a disc-shaped carrier;

Figure 12 is a side elevation of a grinding device for working the interior of tubes and in which the abrasive tube sections are mounted on levers pivotally connected with a rotary shaft and press the abrasive tube sections against the tube wall under the action of centrifugal force.

Figure 13 shows in longitudinal section a grinding device in which the adjustable abrasive tubes of considerable length are fitted in a driven horizontal cylinder supported at both ends;

Figure 14 is a cross-section through the grinding device illustrated in Figure 13 (without cross-piece according to Figure 16).

Figure 15 shows a support serving as rest for the abrasive tubes and rigidly connected to the outer jacket of the grinding device according to Figure 13.

Figure 16 shows in elevation a cross-piece for simultaneously shifting in longitudinal direction by means of screw spindles a group of abrasive tubes screwed to the cross-piece.

Figure 17 shows the cross-member according to Figure 16 in top plan view.

Figure 18 is a diagrammatic view illustrating a modification of grinding element.

Figure 19 is a similar view illustrating a further modification.

Figure 20 is a partial view of a still further modification showing grinding elements mounted upon a carrier.

Figure 21 is a diagrammatic view showing a tool for moulding tubular abrasive bodies having the cross-sectional shape of circular ring sections with matched narrow spacing webs.

Figure 22 is a partial view illustrating a further modification.

Figure 23 isa side elevation, partly in section, of a grinding device with vertical arrangement of the grinding spindle with relatively short abrasive tubes fitted parallel to the axis of rotation, which can be easily readjusted and fixed by hand and which can in addition take fillings of abrasive material.

Figure 24 is a front elevation, partly in section, of a grinding roll which is composed of annular carriers with radially inserted abrasive tube sections forming a grinding roll set, and

Figure 25 is a side elevation, partly in section, of the grinding roll ilustrated in Figure 24.

In Figures 1 to 6 and 18 to 22 the cross-sections through the tubular grinding tools, which are preferably composed of Wound fabric webs bound with synthetic resin, between the metallic or non-metallic layers of which hard material grains 2 are embedded under stnong pressure, are designated by 1. Only in Figure 1 are the wound fabric webs also shown in section. As illustrated in Figures 2 and 6, elongated abrasive bodies 3 can be additionally introduced into the tubular abrasive bodies 1 and may also be composed of wound, highly compressed fabric webs impregnated with abrasive grit. If the wound tubes are compressed by four radially arranged rams, lugs are also formed as shown in Figure 2, which lugs enable the abrasive body 3, which is also of tubular shape, to be fitted in the grinding tube 1 in such a manner that gaps or spaces remain and serve for removing chips and feeding loose grit. The cross-section of the additionally inserted elongated abrasive bodies 311, 3b, and 30 may, as shown in Figures 3, 4 and 6 respectively, also be of rectangular, star or even triangular shape respectively. Any cross-sectional shape can be chosen in order to increase s the efiective volume of the grinding tube 1 by means of such insertions carrying additional abrasive material.

According to Figure additional tubes 3 to 3" of smaller diameter can be inserted in the grinding tube 1 and also serve for enlarging the elfective volume or also for introducing loose abrasive grit. In any case it is necessary to retain free spaces 4, 4" and 4" for leading off the grinding chips produced. As regards the possible crosssectional shapes, Figure 18 shows a tubular grinding body 1a of hexagonal shape. This shape allows the space serving for accommodating the abrasive bodies in a carrier, to be filled in such a manner that the abrasive bodies are side by side. When the tubular grinding body is of rectangular cross-sectional shape as shown in Figure 19 the fabric is first wound with interposed abrasive grit onto a mandrel corresponding to the free cross-sectional, rectangular shape shown in Figure 19. The wound laps must then be subsequently compressed by rams which so act that the longitudinal sides of the rectangular are considerably thickened. By this means 'a particularly high resistance to wear and a firm embedding of the abrasive particles are obtained in these zones. The above mentioned compressing opperation can be attained in that the sides 48 of the rectangle producing the cross-connection, have not the same high degree of compactness as the other sides, so that they wear away more quickly during the grinding operation with the result that the longitudinal sides are exposed. Similar conditions can be produced in the case of the tubular grinding bodies having a crosssection in the shape of a circular ring section as shown in Figures 20 to 22. These grinding tubes having a crosssectional shape of a ring section (see Figrue 20) can be arranged side by side on a carrier disc so that grinding paths with the same curvature radius are produced. Also in this instance, when a compressing tool as shown in Figure 21 is used, greater wear will occur during the grinding operation in the regions of the connecting webs or arms 48, so that the surface of the arms 48 will always hear slightly below the grinding surface of the slightly curved longitudinal sides representing the actual grinding path.

The compression can be eifected in the manner shown in Figure 21 by guiding the rams 45 and 46 in the pressing tool 47 so that they compress the laps wound on a curved mandrel. At the same time the greatest pressure is not transmitted between the two curved longitudinal sides so that the above-mentioned wearing elfect takes place.

If the lower die or ram 46 is shaped as shown in Figure.

21, the spacer arms 44 are formed at the same time during the pressing operation and these arms, according to Figure 22, enable a plurality of grinding bodies with crosssection of circular segmental shape to be arranged one above the other, with the result that uniform spacing of the curved paths can be maintained. According to Figure 22, recesses are provided in the rotary carrier 5a for receiving a plurality of superposed tubular abrasive bodies with circular ring-section-shaped cross-section which are held in these recesses in the carrier So by the exertion of pressure (50). Furthermore, the above-described tubular grinding bodies can also be interconnected by plastic plates or metal plates 49'.

The tubular grinding bodies 1 can be inserted in the carrier 5 as illustrated in Figures 7 and 8. In this case the central axes of 1 lie in the same pitch circle. The carrier body 5 is provided with a bore 7 so that it can be slipped on to grinding spindles. The grinding plane is designated by 22 in Figure 8. The tubular grinding bodies 1 can also be set at an angle to the axis of rotation of the carrier 5, as shown in Figure 9. It is possible with this arrangement to surface-grind the walls of bores, for example of tubes. Instead of the four grinding tubes shown in this figure, it is evident that a greater number of grinding tubes can be fitted in the carirer 5'. If the holders 10 for the tubular grinding bodies 1, shown in Figure 10, are slidable in a radial guide 9, the diameter of the pitch 6 circle of the grinding tubes 1 can be varied by the radial displacement of these grinding tubes by means of flat spiral-s 13 worked in a ring 12 rotatable in relation to the carrier 5". The holders 10 are connected with the flat spirals 13 through the intermediary of intermediate members 11. If the tubular grinding bodies are of relatively great length, two rings 12 and two flat spirals 13 are provided in the carrier 5", which for this purpose is made of cylindrical shape, so that the holders provided for the front and rear ends of the tubes, as well as the grinding tubes fitted therein, carry out a radial parallel displacemerit in relation to the axis of rotation of the carrier 5".

In addition to the axially parallel and inclined arrangements of the tubular grinding bodies 1 according to Figures 7 to 9, grinding tube sections may be employed arranged as shown in Figure 11, so that they can be fitted on pins 14 connected to the carrier ring 5" by means of a screw-threaded extension 15. The grinding tube sections 1 can be fixed on the pins 14 by means of transverse pins, by known internal clamping devices or by providing the pin 14 and also the bore of the grinding tube sections 1 with screw threads. has a bore 7 and rotates about the central axis shown in Figure 11. By profiling the guiding tube sections 1 fitted on the pins 15 it is possible to surface-grind workpieces having a certain, for example, curved profile.

If bores, for example the inner Wall 21 of a cylinder (20), are to be ground, the grinding tube sections 1 may, according to Figure 12, be mounted on two or more onearmed levers 18 and 19, which are connected by a hinge 17 with the rotary driving shaft 16 running at a high speed, so that, during the rotation, the grinding tube sections 1 are pressed by the centrifugal effect in the direction of the arrows against the tube wall. During the grinding of the wall 21 of a tube having a diameter D, the whole grinding wheel must carry out a feed movement in the direction of the arrow S. As hereinafter set forth in the description of Figures 24 and 25, the internal grinding of tubes can also be carried out with grinding rolls which can likewise be varied as regards their effective diameter.

In Figures 13 to 17 a construction for grinding the outer wall of tubes is shown by way of example as an embodiment of the invention. Seeing that in this case large quantities of material have to be removed, it is necessary to employ tubular grinding bodies of great length. These tubes 1 having an initial length of 1 metre and more are placed in a cylindrical grinding construction (Figure 13) which consists substantially of the following parts: The outer casing 23 made from very resistant steel, the carrier tube 27, the four spacers 28 for establishing a firm connection between 23 and 27, covers 25 and 26 fitted in the ends, the shaft 35 centrally arranged in the construction and which does not participate in the rotation, the roller bearings 34, the pillow blocks 36 which are bolted to the sliding carriage 39 and the supports 24 rigidly connected with the outer casing 23 and serving as bearing surface for the grinding tubes I acted upon by centrifugal force (see also Figure 15).

The tubular grinding bodies 1 arranged in groups of three (in Figures 14 to 17), are secured to a cross-piece 42 by means of screws 43, which cross-piece is guided on the carrier tube 27, the spacers 28 and the profile of the support 24 facing the axis of rotation (see Figures 13 and 16).

According to Figure 17, the cylindrical members 29 are inserted in the grinding tubes 1 so that they can be secured by screwing. -Each four groups of grinding bodies are fitted in the grinding construction according to Figures 13 and 14. With the aid of screw spindles 30, carrying pins 31 at both ends, and of an epicyclic gear 32/33, the tubular grinding bodies 1 can, on being simultaneously and uniformly turned in the construction, be shifted in axial direction and so adjusted that a small portion of the grinding bodies 1 projects from the cover 25 facing the tube 38 to be ground. For grinding the The carrier ring 5" cylindrical outer wall or jacket of tubes the Working sur faces 22 of the tubular grinding bodies 1 are so profiled that a larger surface of the bodies 1 contacts the outer wall or jacket of the tube 38 to be ground. As continuous wear takes place during the grinding operation, the tubular bodies must be periodically or continuously readjusted by means of the constructional elements 30, 32, 33 and 42. 'In the case of periodic displacement of the bodies 1, the feeding movement must be effected by the carriage 39 carrying the construction and which can be coupled with a precision spindle.

- The amount of adjustment of the grinding construction according to Figure 13 in relation to the horizontal central axis of the tube 38 to be surface ground, must be effected in such a manner that the greatest efiective diameter'of the tubular grinding body 1 is located in the middle. The grinding construction can be driven by means of a belt 37. The speed must be such that the grinding tools 1 operate at an average working speed of 90 metres per second.

The grinding device 5b with vertically arranged grinding spindle 53 illustrated in Figure 23, has a relatively large number of axially parallel bores 63 of the same pitch circle diameter, in which bores the tubular grinding bodies 1 are inserted by hand. The grinding spindle 53 is held, for example, in the arm (62) of the grinding machine by clamping. The tubes I inserted by hand are allowed to rest on the surface 22 to be ground when the machine is at a standstill and are then clamped, for example, by means of hydraulically operating pressure means built up in the following manner:

A piston 57 arranged radially in front of each grinding tool 1 can be moved by pressure fluid which is fed via the passages 58, 60 and 61. The annular recess 58 turned in the grinding device 5b is closed by means of a screw ring 59. The centrifugal forces occurring at the speed of rotation necessary for the grinding device 5b also produce an amply tight seating of the tubes 1 inserted by hand. The surfaces of the bore 63 against which the grinding tools 1 are pressed by centrifugal effect are preferably provided with transverse grooves, screw threads, roughened surfaces and the like, and similarly a portion of the outer wall of the tubular grinding tools. With this type of holding means for the grinding tools 1 a slight stress, for example spring pressure, is sufficient once the tools have been inserted in the carrier 5b. For fixing the grinding tubes 1 in the grinding device Sb any of the known clamping arrangements can be employed, including those using plastic agents, such as neoprene.

The grinding device is mounted on a conical pin 54 formed on the grinding spindle 53 and there held by means of screw 55 with interposed washer 56.

The spaces 63 for receiving the tubular grinding tools 1 may be of any desired cross-sectional shape, for example also for taking those having the cross-sectional shape of circular ring segments or sections such as those shown in Figures 20 and 22.

For the economical chip removal of large volumes of material, for example when surface grinding metal sheets, as shown on the right-hand side of Figure 23, provided it 1s a question of unbroken surfaces from which the grinding device is not raised during the grinding operatron, cartridges enclosed in thin, easily worn away casings 69 and filled with accurately dosed quantities of loose abrasive grit 68 are inserted in the tubular grinding bodies and pressed under elastic pressure against the surface 22 to be ground, for example by means of an air cushion or bag 7t) which can be supported by a disc. 71 fixed by a cross-pin 67. A valve 72 ensures that a certain pressure is maintained in the bag 7 0.

At the beginning of the grinding operation, the portion of the thin casing of the cartridge facing the surface of the workpiece will naturally be rubbed away, so that the abrasive grit 69 is exposed and becomes effective.

These abrasive grit cartridges may also be of any desired cross-sectional shape, so that they can likewise be introduced into the free cross-sectional spaces in the grinding tubes 1c, as shown for example, in Figure 20. The abrasive grit of the cartridges may, as already mentioned in the introduction to the specification, be held in light bond by various means to enable the grinding device to be, if necessary, lifted off the surface of the workpiece during the grinding operation.

Whereas the grinding device shown in Figure 11 has a carrier ring 5" which is wider than the largest diameter of the grinding tube sections I slipped on to the plugs or pins 14, the carrier rings 5r, 5s, 5!, and 5;: of the construction illustrated in Figures 24 and 25 are only of a width corresponding to the internal diameter of the grinding tube sections 1. Also in this case these latter are slipped on to the pins or plugs 14 which are screwed into the carrier ring by means of screw-threaded extensions 15 or are made integral therewith. The bodies 1 may be fixed on the pins 14 by cross-pins 66, by an internal clamping arrangement not shown on the drawing or by screw threads which would have to be provided on the pins 14 and in the bores of the bodies 1. Owing to the narrow width of the rings 5r, 5s, 5t, and 5a it is possible toassemble and unite the individual grinding devices, composed of the ring and the plugs or pins 14 connected therewith, with the grinding tube sections I slipped thereon, to form sets (5r, 5s, 5! and Sr: and so forth) by means of a centrally arranged shaft 64 and a ring nut 65, so that a grinding roll is produced, the width of which can be adapted to the surface of the workpiece to be ground.

The grinding tube sections of the carrier ring 5.9 (Fig. 25) are, as indicated by the references 51 and 52, displaced, for example, through an angle of 30 in relation to the position of the grinding ring sections 1e, 1f, 1g and 1h (the last position is not shown in the drawing) of the carrier ring 5s, so that uniformity is ensured during the grinding operations by means of the roll and also, by the staggered arrangement, the power consumption shows no unnecessary fluctuation during the grinding operation. The narrow width of the carrier rings 5s allows an overlapping of the grinding paths so that no steps or irregularities are produced on the surface worked.

By the application of suitable measures, for example, by using a mandrel tapering in the axial direction of the grinding roll or a conical sleeve, it is possible to change the effective external diameter of the grinding roll by radially shifting the plugs or pins 14, so that the diameter of the roll can be adapted to the diameter of bores, for example of tubes. Readjustment as the grinding tube sections of the grinding roll wear down is also rendered possible by this means.

The abrasive grit cartridges mentioned in the description of Figure 23 can also be inserted in the free apertures in the grinding tube sections both of the grinding device according to Figures 24 and 25 and also of that shown in Figuire l2, seeing that unbroken surfaces also come into question in the case of internal grinding of the tubes. Thus new methods of grinding the inner wall of tubes are offered by the invention.

Finally it is also pointed out that the bonding material of the tubular grinding bodies can be the same as that of the grinding wheels which are already known. As the end of the tube directed towards the surface to be ground only extends a small amount from the carrier and the tube bears on practically its entire length within the carrier, the centrifugal forces produced at the high speeds of rotation are taken up by the carrier itself, so that, in addition to the very tightly wound tubes with plastic bond, tubes can also be used which are produced, for example, by saturating with thermosetting synthetic substances into which the abrasive particles can also be introduced in the form of a tube, if desired adding afew laps of very strong steel wire fabric, whereupon the bond is established by p fiisure saturation.

The fact that the centrifugal forces which occur are absorbed by the carrier also enables the use of the known vitrified bonds even in the case of tubular grinding bodies of relatively great length. Also in this case, all the crosssectional shapes mentioned in the preceding specification can be employed. A combination of different kinds of bonds is likewise possible so that, for example for reasons of the total bending strength, the outer tube 1 according to Figure 5 can be composed of wound fabric webs bonded with synthetic resin, whereas the inserted tubular grinding bodies 3 may have a vitrified bond.

I claim:

1. Thin-walled tubular grinding tool formed from thermosetting synthetic resin saturated, wound and heavily compressed fabric webs with abrasives embedded therein, said tubular grinding tool having a cross-section in the form of a rectangle, the longitudinal sides of said rectangle having a higher degree of compactness than the transverse sides.

2. Thin-walled tubular grinding tool formed from thermosetting synthetic resin saturated, wound and heavily compressed fabric webs with abrasives embedded therein, said tubular grinding tool having a cross-section in the form of a circularly curved rectangle, the longitudinal sides of said rectangle having a higher degree of compactness than the transverse sides.

3. Thin-walled tubular grinding tool as set forth in claim 1 wherein small spacer arms are provided, said arms being prolongations of said transverse sides.

4. Thin-walled tubular grinding tool as set forth in claim 2 wherein small spacer arms are provided, said arms being prolongations of said transverse sides.

References Cited in the file of this patent UNITED STATES PATENTS 293,398 Barclay Feb. 12, 1884 904,805 Pierce Nov. 24, 1908 970,619 Gardner Sept. 20, 1910 1,951,977 Hanus Mar. 20, 1934 FOREIGN PATENTS 580,330 Great Britain Sept. 4, 1946 1,147,042 France Nov. 18, 1957 787,689 Great Britain Dec. 11, 1957 

